$\mathrm{S}_3 \times \mathrm{C}_{12}$ in dimension 4
This tangent representation satisfies the necessary conditions for a hyperelliptic fourfold, but it is not known whether it is realized by an actual variety. See completeness in dimension 4.
- holonomy group
- $\mathrm{S}_3 \times \mathrm{C}_{12}$, order $72$, SmallGroup $[72,27]$ · character table
- tangent representation $\rho$
- $\rho(g_{1}) = \operatorname{diag}(1, 1, -1, -1)$$\rho(g_{2}) = \operatorname{diag}(1, i, -1, -1)$$\rho(g_{3}) = \operatorname{diag}(1, 1, \zeta_{3}, \zeta_{3})$$\rho(g_{4}) = \operatorname{diag}(1, 1, 1, -1)$$\rho(g_{5}) = \operatorname{diag}(1, 1, \zeta_{3}, \zeta_{3}^{2})$
- order of $\omega_X$
- 12
- number of moduli
- 1
- irregularity $q = \dim \operatorname{Aut}^0(X)$
- 1
- Albanese
- the Albanese variety has dimension $1$; the general fiber has dimension $3$ and is an abelian variety or a hyperelliptic variety (details)
- $\mathbf{D}^{\mathrm{b}}(X)$
- indecomposability open (why)
- Hochschild cohomology $\dim \mathrm{HH}^\bullet$
- $(1, 2, 1, 0, 0, 0, 0, 0, 0)$
Hodge diamond
1
1 1
0 3 0
0 2 2 0
0 0 4 0 0
0 2 2 0
0 3 0
1 1
1
1 1
0 3 0
0 2 2 0
0 0 4 0 0
0 2 2 0
0 3 0
1 1
1
polyvector fields $\mathrm{H}^q(X,\bigwedge^p T_X)$
1
11
010
0000
00000
0000
000
00
0
11
010
0000
00000
0000
000
00
0
twisted Hodge numbers $\mathrm{h}^{p,q}(X,\omega_X^{\otimes j})$
Since $\operatorname{ord} \omega_X = 12$, the twists by powers of the canonical bundle form a finite package of $12$ diamonds (explained).
$\omega_X^{\otimes 0}$
1
11
030
0220
00400
0220
030
11
1
11
030
0220
00400
0220
030
11
1
$\omega_X^{\otimes 1}$
0
00
000
0001
00011
0001
000
00
0
00
000
0001
00011
0001
000
00
0
$\omega_X^{\otimes 2}$
0
00
000
0000
00000
0000
000
00
0
00
000
0000
00000
0000
000
00
0
$\omega_X^{\otimes 3}$
0
00
000
0100
01100
0100
000
00
0
00
000
0100
01100
0100
000
00
0
$\omega_X^{\otimes 4}$
0
00
000
0000
00000
0000
000
00
0
00
000
0000
00000
0000
000
00
0
$\omega_X^{\otimes 5}$
0
00
000
0100
01100
0100
000
00
0
00
000
0100
01100
0100
000
00
0
$\omega_X^{\otimes 6}$
0
00
000
0000
00000
0000
000
00
0
00
000
0000
00000
0000
000
00
0
$\omega_X^{\otimes 7}$
0
00
000
0010
00110
0010
000
00
0
00
000
0010
00110
0010
000
00
0
$\omega_X^{\otimes 8}$
0
00
000
0000
00000
0000
000
00
0
00
000
0000
00000
0000
000
00
0
$\omega_X^{\otimes 9}$
0
00
000
0010
00110
0010
000
00
0
00
000
0010
00110
0010
000
00
0
$\omega_X^{\otimes 10}$
0
00
000
0000
00000
0000
000
00
0
00
000
0000
00000
0000
000
00
0
$\omega_X^{\otimes 11}$
0
00
000
1000
11000
1000
000
00
0
00
000
1000
11000
1000
000
00
0
References
- A. Demleitner, The classification of hyperelliptic groups in dimension 4. arXiv:2211.07998
- A. Demleitner, C. Gleissner, The classification of rigid hyperelliptic fourfolds, Ann. Mat. Pura Appl. (4) 202 (2023) 1425–1450. MR4576947 doi
- P. Belmans, A. Demleitner, P. Núñez, The Albanese morphism for hyperelliptic varieties, Indag. Math. (N.S.) 37 (2026) 1450–1475. MR5103244 doi